1. Field of the Invention
This invention generally relates to methods and apparatuses for towing multiple streamer array systems
2. Background
One of several conventional techniques for marine seismic surveying is to tow a number of hydrophones behind a vessel over the survey area. Typically, the hydrophones are contained in one or more cables called streamers. Seismic impulses are created and their reflection from the sea bottom and the underlying strata is received by the hydrophones. This data is then used to image the sub-sea strata. Because it is advantageous to extend the hydrophone pattern over a large portion of the survey area, several streamers are towed at the same time.
FIG. 1 illustrates a conventional streamer configuration from an aerial view. Conventional streamer configurations use a vessel 1 to pull streamers 2. Paravanes 3 are used to keep the multiple streamers 2 separated. The paravanes 3 pull various lead in cables 7 and other cables 8 laterally away from the vessel 1. Use of the paravanes and the configuration of the lead-in cables (or spreader cables) 7 and superwide cables 8 enables several streamers 2 to be pulled from a single vessel 1 in a wide pattern. However, the more lead-in 7 and other cables 8 used, the more drag the vessel 1 and the streamers 2 experience. Drag increases fuel and vessel power requirements.
Another drawback of conventional techniques is that to connect the various components of conventional cable configurations, the cables 7, 8, are cut and then spliced together. This includes the stress bearing members, the seismic data conductors, and the electrical power conductors. By cutting and then splicing, the mechanical integrity of the cable is compromised, and the cables become more susceptible to fatigue and/or manufacturing process induced failure. Also, if optical fibers are used for transmitting the data from the sensors to the vessel, each splice will attenuate the signal and will give a substantial loss in signal level.
Thus, there is a long felt need for an improved method and system for towing streamers which increases reliability, reduces components, reduces structural, electrical, and optical splices, and that creates less drag than conventional techniques.